The top Republican challenger to Alabama Sen. Richard C. Shelby said Tuesday the fifth-term lawmaker is starting to show signs of concern, two weeks before the March 1 primary.

Jonathan McConnell, a businessman and ex-Marine who is the leading pack of Republican trying to unseat Shelby, began to feel the wrath of the incumbent's $17 million campaign fund last week when he became the target of a blistering online effort.

The move, McConnell told Roll Call, shows "he's definitely worried that we're going to get to a runoff."

After Shelby's campaign had stayed positive with a $6 million, three-month positive television and radio campaign, it finally shot back at McConnell with a new website, ConManJon.com . There, Shelby accused him of being everything from a “crony capitalist” to a “pro-amnesty liberal.”

Of the website, McConnell said, "I don’t think the people of Alabama are buying it." In fact, he said he was so amused by it that he planned to order t-shirts for his campaign staff to wear on election night bearing an image of the “Con Man Jon” character.

In addition to the negative messaging against McConnell, Shelby has upped his conservative rhetoric ahead of the primary. In an email to supporters following the death of Supreme Court Justice Antonin Scalia, the Shelby's campaign said he "will stop Obama from nominating a liberal radical that will ignore our Constitution."

McConnell admitted his campaign still has work to do, but he said his internal polling had shown Shelby dipping closer to the 50 percent required to avoid a runoff. Shelby’s campaign has released a poll of its own showing him well above the requirement. No independent polling has yet been released.

Regardless, McConnell said he feels emboldened by Republican candidates Donald Trump and Texas Sen. Ted Cruz holding a lead in the state. He said his goal in the March 1 primary is simple: Push Shelby below 50 percent and ride Trumps's and Cruz's antiestablishment coattails into a runoff.

McConnell said his candidacy is one of a “change agent” like supporters of Trump or Cruz might support. “Are people in Alabama going to cancel out that vote by voting for Richard Shelby who represents the status quo?”

McConnell, whose campaign brought in $586,500 in the last quarter of 2015, ended the year with less than $300,000 in the bank after donating $255,000 and loaning $36,500 to his own campaign . Speaking during an interview from his car in between fundraising calls on Tuesday, McConnell said the financial disadvantage is one that is a symptom of running against a lawmaker as established as Shelby.

In addition to his own large campaign fund, Shelby has the support of the party’s establishment in Washington. He has been endorsed by the National Rifle Association, fellow Alabama Sen. Jeff Sessions and the Alabama Republican Assembly. (The Alabama Republican Party, however, "does not get involved in primaries," chairman Terry Lathan said.)

When asked about the race, Ward Baker, the executive director of the National Republican Senatorial Committee, said flatly last week, “He’s going to win."